Simultaneous multi-alloy casting

ABSTRACT

A method of casting a multi-layered metal ingot including the steps of delivering a metallic divider member into a direct chill mold, pouring a first molten metal into the mold on one side of the divider member, and pouring a second molten metal into the mold on the other side of the divider member, and allowing the first molten metal and the second molten metal solidify to form a metal ingot which includes the divider metal layer disposed there between.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is a divisional of application Ser. No.10/004,041, filed Oct. 23, 2001, entitled “Simultaneous Multi-AlloyCasting

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to the simultaneous casting ofmultiple alloys, in particular, direct chill casting of multiplealuminum alloys using a metallic member between the alloys to form amulti-component cast product and/or the use of a metallic member as anexternal layer on a cast ingot.

[0004] 2. Prior Art

[0005] In the production of aluminum alloy ingots by a conventionaldirect chill (DC) casting process, molten aluminum is poured into anopened end mold. The lower end of the mold is initially closed by aplatform referred to as bottom block and the molten metal pools withinthe mold. The bottom block is progressively lowered in step with thepouring of the molten metal. The wall of the DC mold is continuouslycooled so that a solid skin of metal forms in contact with the mold wallat the level of the surface of the pool of molten metal in the mold. Anexample of the method of DC casting is described in U.S. Pat. No.4,071,072, incorporated herein by reference. In this conventionaloperation, a single molten aluminum alloy is direct cast into an ingot.

[0006] Such aluminum ingots are often times incorporated with otheralloys to form a composite product. For example, brazing sheet for theheader of a heat exchanger or for reinforcement structures may beproduced from an Aluminum Association (AA) 3000 series aluminum alloywith a clad layer of an AA 4000 series alloy. Evaporator sheet productor plate type heat exchangers typically include a 3000 series alloy cladon both sides with a 4000 series alloy. Likewise, radiators often areformed from a 3000 series alloy with a 4000 series cladding andwater-side liner of an AA 1000, 5000, 6000, or 7000 series alloy. Theclad layer is conventionally roll bonded in plate form onto an ingot ofthe core alloy (e.g., a 3000 series alloy). Roll bonding requiresmultiple rolling passes, scalping, reheating, and sealing steps toproduce the clad alloy in sheet form. Each of those processes adds tothe cost of the final clad product. In addition, the thickness ofcladding produced via roll bonding is generally limited to a maximum ofonly about 35% of the total sheet thickness. Roll bonding can also beextremely difficult if the mechanical properties of the alloys beingroll bonded are too dissimilar at the rolling temperatures. For example,when one alloy deforms very easily while the other alloy does not, thealloys do not seal properly or the target cladding ratio is off.

[0007] More recently, attempts have been made at casting composite metalproducts. One such process is described in DE 4420697 in which one alloyof a billet is DC cast on one side of a fixed barrier and another alloyis DC cast on the opposite side of the barrier. The process iscontrolled such that the two molten metals come in contact with oneanother while in the molten state to provide a controlled mixing of thetwo melts. In this manner, the composition of the composite billet inthe direction perpendicular to the contact surface of the two metalcomponents changes continuously. The concentration of the individualalloy elements changes continuously from the values of one alloy to thevalues in the other. The fixed barrier maintains the two componentsapart from each other within the mold, and the barrier is positioned offcenter so that one component is narrower than the other. The alloyclosest to the mold (the narrower component) cools and solidifiesearlier in the process than the other alloy, i.e., at a great heightfrom the bottom block. The bottom block is withdrawn at a speed wherebythe levels of the melts within the mold remain approximately even.Although one alloy solidifies before the other alloy, there is a smallregion between the melts in which the melts are able to flow into oneanother and mix briefly to promote adhesion between the two alloys.While this method provides some adhesion between the two components ofthe cast product, the mixing of the components which occurs during thecasting can be detrimental to the finished product. The location andshape of the fixed barrier are also critical to avoid intermixing of themolten alloys. The properties of the alloys simultaneously cast in thismanner may be affected by the mixing of the alloying components. Thismethod also requires careful control of molten metal flow to avoidmixing due to hydraulic pressure differences as well as careful controlof the solidification rate of the alloy forming the narrower componentto ensure only brief mixing of the alloys in the region immediatelybelow the barrier.

[0008] Another method of DC casting a composite ingot is disclosed inU.S. Pat. No. 4,567,936 in which an outer layer is simultaneously castwithin an inner component. According to this method, the outer layersolidifies prior to contact within the molten inner alloy. This avoidsmixing between the components of the inner component and the outerlayer. A drawback to this method is that the outer layer must solidifycompletely before the inner alloy can be cast within the outer layer.The thickness of the outer layer also is limited because the heat of theinner component must exit through the outer layer to the exteriorsurfaces of the cast product. Hence, the configuration of the finalmulti-component product also is limited.

[0009] Accordingly, a need remains for a method of simultaneouslycasting a multi-alloy metal product with a minimum of mixing between thealloys of the product and which can produce cast metal products in avariety of configurations.

SUMMARY OF THE INVENTION

[0010] This need is met by the method of the present invention ofcasting a multi-layered metal ingot including the steps of delivering ametallic divider member into a direct chill mold, pouring a first moltenmetal into the mold on one side of the divider member and pouring asecond molten metal into the mold on the other side of the dividermember, and allowing the first molten metal and the second molten metalto solidify to form a metal ingot which includes the divider metal layerdisposed between the two cast layers. The multi-layered metal ingotremoved from the mold contains at least two cast layers including thefirst and second metals separated by a layer of the divider member.Alternatively, the divider member may be positioned against a wall ofthe mold and a single molten metal is poured into the mold to produceone cast layer bound to the divider member thereby forming an outershell or cladding on the ingot. The divider member may be a sheet havinga thickness of up to about 0.25 inch or a plate having a thickness of upto about 6 inches. The position of the divider member may be shiftedwithin the mold to produce varying thicknesses of the cast metals. Morethan one divider member may be placed in the mold with molten metalspoured on opposite sides of each divider member to produce a metalproduct having at least three cast layers separated by the dividermembers. The fundamental principles guiding the attainment of a stronglybonded interface between the divider member and the molten metal areidentical regardless of where the divider member is located within theingot. The divider member may also be tubular in shape. One metal ispoured into the tubular divider member while another metal is pouredbetween the tubular divider member and the mold.

[0011] The molten metals may each be an alloy of AA series 1000, 2000,3000, 4000, 5000, 6000, 7000, or 8000. The divider member may be a solidmetal that will survive exposure to the molten aluminum during thecasting operation. For the purpose of maintaining a “clean” scrap loop,the divider member preferably is aluminum or an aluminum alloy or a cladaluminum product that has a solidus temperature greater than theliquidus temperatures of the alloys cast on either side thereof. It ispreferred that the solidus temperature of the divider member be at least610° C. A particularly suitable metal for the divider member is an AA1000 series alloy. Alternatively, the divider member may be in the formof a screen alloys of iron, titanium, magnesium, copper, or nickel.

[0012] A complete understanding of the invention will be obtained fromthe following description when taken in connection with the accompanyingdrawing figures wherein like reference characters identify like partsthroughout.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a partially sectioned schematic of an apparatus forsimultaneously producing a composite metal product having two castlayers according to the present invention;

[0014]FIG. 2 is a cross-section of the metal product produced in theapparatus shown in FIG. 1;

[0015]FIG. 3 is a partially sectioned schematic of an apparatus forproducing a composite metal product having one cast layer according toanother embodiment of the present invention;

[0016]FIG. 4 is a cross-section of the metal product produced in theapparatus shown in FIG. 3;

[0017]FIG. 5 is a partially sectioned schematic of a device forsimultaneously producing a composite metal product having three castlayers according to the present invention;

[0018]FIG. 6 is a cross-section of the metal product produced using thedevice shown in FIG. 5;

[0019]FIG. 7 is a cross-section of the metal product produced in thedevice shown in FIG. 1 with additional layers roll bonded thereto;

[0020]FIG. 8 is a cross-section of the metal product produced in thedevice shown in FIG. 5 with a layer roll bonded thereto;

[0021]FIG. 9 is a cross-section of the metal product produced accordingto the present invention wherein the thickness of the layers of thecomposite product is not constant across the width of the product;

[0022]FIG. 10 is a cross-section of the metal product of FIG. 9following a rolling step;

[0023]FIG. 11 is a partially sectioned schematic of another device forsimultaneously casting multiple alloys to produce a billet using atubular divider member;

[0024]FIG. 12 is a cross-section of the device shown in FIG. 11 takenalong lines 12-12;

[0025]FIG. 13 is a cross-section of the billet produced in the deviceshown in FIG. 11;

[0026]FIG. 14 is a photograph of a cross-section of an ingot producedaccording to the present invention;

[0027]FIG. 15 is a photomicrograph of a portion of the ingot shown inFIG. 14;

[0028]FIG. 16 is a photomicrograph of a portion of the ingot shown inFIG. 14 after hot rolling;

[0029]FIG. 17 is a photomicrograph of the portion of the ingot shown inFIG. 16 after cold rolling;

[0030]FIG. 18 is a photograph of a cross-section of another ingotproduced according to the present invention;

[0031]FIG. 19 is a photograph of a cross-section of yet another ingotproduced according to the present invention; and

[0032]FIG. 20 is a photomicrograph an interface between the layers ofanother ingot produced according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] For purposes of the description hereinafter, the terms “upper”,“lower”, “right”, “left”, “vertical”, “horizontal”, “top”, “bottom” andderivatives thereof shall relate to the invention as it is oriented inthe drawing figures. However, it is to be understood that the inventionmay assume various alternative variations and step sequences, exceptwhere expressly specified to the contrary. It is also to be understoodthat the specific devices and processes illustrated in the attacheddrawings, and described in the following specification, are simplyexemplary embodiments of the invention. Hence, specific dimensions andother physical characteristics related to the embodiments disclosedherein are not to be considered as limiting.

[0034] The present invention is directed to a method of casting amulti-layered metal ingot and the product produced thereby. The methodof the present invention uses an apparatus 2 schematically shown in FIG.1 which incorporates a conventional direct chill mold 4. The directchill mold 4 defines a water chamber 6 and a slit 8 through which wateris emitted directly onto the surface of an ingot 10 emerging from themold 4. The cast ingot 10 solidifies on a bottom block 12.

[0035] A metallic divider member 14 is suspended into the mold 4 andseats on the bottom block 12. The metallic divider member 14 provides abarrier between a first molten metal 16 which is fed into the mold 4 viaa first trough 18 and a second molten metal 20 fed into the mold 4 via asecond trough 22. The bottom block 12 is withdrawn in the direction ofarrow A while coolant (water) is applied to the surfaces of the ingot10. Suitable speeds for the bottom block 12 are about 1 to about 6inches per minute, preferably about 2 to about 3 inches per minute. Whenciting such ranges herein, the range includes all intermediate values.The divider member 14 remains in contact with the bottom block 12 andaccordingly travels downwardly at the speed that the bottom block 12travels. A crane (not shown) equipped with movable grips (e.g., wheels)may be used to suspend the divider member 14 over the apparatus 2 anddeliver the divider member 14 into the mold 4. Other mechanisms may beused to suspend and deliver the divider member 14 into the mold 4.

[0036] Each of the first and second molten metals 16 and 20 solidify asgenerally shown in FIG. 1. The portion 24 of the metal 16 closest to themold 4 solidifies very quickly, e.g. in less than about 10 seconds.Solidification of the metal 20 likewise occurs at a region 26 adjacentthe mold 4. Semi-solid zones 28 and 30 form below the level of therespective first solidification regions 24 and 26. The metals 16 and 20also begin to solidify adjacent the divider member 14 at respectivelocations 32 and 34. The locations 24, 26, 32 and 34 may be at the sameheight as each other or at different heights from the bottom block 12.In many cases, the melting point of the metal of the divider member 14is less than the temperature of the incoming molten metals 16 and 20.Nevertheless, the divider member 14 does not completely melt and servesto prevent mixing of the metals 16 and 20 by acting as a heat sink andas an interface between the metals 16 and 20. Some heat from the moltenmetals 16 and 20 transfers into the divider member 14 and subsequentlyis transferred out of the portion 36 of the divider member 14 thatextends up and out of the mold 4. Similarly, some of the heattransferred to the divider member 14 is also subsequently transferredout of the divider member to the solidifying ingot 10 below the moltenmetals 16 and 20. The divider member 14 may experience minimal melting(erosion), but this minimal amount does not affect the metallurgicalproperties of each of the metals 16 and 20 cast on opposing sides of adivider member 14. Upon complete solidification, the metals 16 and 20form respective solid components 38 and 40 separated by the dividermember 14.

[0037] The minimal melting of the divider member 14 provides for somemixing of the components of the divider member 14 with the components ofthe metal 16 on one side and with the components of the metal 20 on theother side. The minimally mixed metals solidify and thereby adhere thecomponents 38 and 40 to the divider member 14. Superior adhesion betweenthe divider member 14 and components 38 and 40 is achieved when thetemperature of the divider member 14 reaches at least the higher of theliquidus temperature of component 38 and the liquidus temperature ofcomponent 40. It is believed that when the divider member 14 initiallycontacts the molten metals 16 and 20, some solidification of the metalsrapidly occurs on the surfaces of the divider member 14. This temporarysolidification is not shown in FIG. 1. Inherent oxides on the surfacesof the divider member 14 generally remain and become entrapped betweenthe divider member 14 and the solidified metal. When the molten metaltemperatures are sufficiently high, the divider member 14 locallyreaches a temperature greater than the liquidus temperature of themetals 16 and 20 and the initially solidified metal remelts as thedivider member 14 travels in the direction of the arrow A. The dividermember 14 is then directly exposed to the molten metals 16 and 20 andthe oxide destabilizes with some minimal melting of the divider member14. As the divider member 14 continues downwardly, the localtemperatures of the molten metals 16 and 20 decrease to their liquidustemperatures and solidification begins. The local temperatures continueto drop until the solidus temperatures are reached and the alloys fullysolidify resulting in strong bonds between the components 38 and 40 andthe respective sides of the divider member 14.

[0038] Alternatively or in addition thereto, flux may be applied to oneor both sides of the divider member 14. The flux may be applied to thedivider member 14 directly (e.g. by coating the surfaces of the dividermember 14 with flux) or flux may be applied to the upper surfaces of themolten metals 16 and 20 that pool in the mold 4. Immediately prior tocontact between the divider member 14 and the molten metals 16 and 20,the flux melts and chemically reduces oxides on the divider member 14which could otherwise interfere in the adhesion of the molten metals 16and 20 to the divider member 14. Suitable flux includes potassiumaluminum fluoride based fluxes (e.g. Nocolok®) along with but notlimited to fluxes based on cesium-potassium aluminum fluoride basedfluxes and cesium fluoroaluminate based fluxes. The flux may be anymaterial capable of removing the oxide layer by chemical reaction priorto contact of the molten metals 16 and 20 with the divider member 14.When flux is used, lower molten metal temperatures should be used duringcasting to reduce the risk of melting the divider member 14 yet achievestrong adhesion of the components 38 and 40 to the divider member 14.

[0039] A cross section of the ingot 10 produced in the apparatus 2 isshown in FIG. 2. The ingot 10 is depicted as having a rectangularconfiguration with the divider member 14 positioned centrally betweenthe layers of components 38 and 40. However, the divider member 14 maybe positioned off-center and may be as close as about 0.5 inch from sidesurfaces 42 and 44 of the ingot 10. The divider member 14 has a widthbetween edges 46 and 48 thereof which is slightly smaller than the widthof the ingot 10 between edges 49 a and 49 b. Edges 46 and 48 preferablyare positioned about 0.1 to about 3 inches from the mold 4 and are shownnot to scale in FIGS. 2 and 6-8. The cooling rates are highest near thesurface of the ingot 10, and the molten metals 16 and 20 rapidlysolidify at the surface of the ingot. The rapid solidification of moltenmetals 16 and 20 around the edges 46 and 48 minimizes opportunities formixing of the molten metals 16 and 20. Nevertheless, some minimal mixingmay enhance adhesion of the solid components 38 and 40 together. In anyevent, the edges 49 a and 49 b of the ingot 10 are typically trimmed offduring rolling to eliminate edge cracking so these areas of intermixingaround the edges 46 and 48 of the divider member 14 generally arediscarded.

[0040] The thickness of the divider member 14 may range between about0.07 inch to about 0.25 inch (referred to as a sheet) or over about 0.25inch to about 6 inches thick (occasionally referred to as a shlate whenup to one inch thick and generally referred to as a plate when up to 6inches thick). The thickness of the divider member 14 preferably isabout 0.5 to about 6% of the thickness of the ingot 10, more preferablyabout 1 to about 3% of the thickness of the ingot 10. A thinner dividermember 14 may be used when the risk of melting of the divider member 14is low and/or the desired metallurgical or structural properties of theingot 10 dictate that the layer 14 has a minimal thickness. Conversely,a thicker divider member 14 may provide a more significant barrier tomixing of the molten metals 16 and 20 and may serve as one layer in amulti-layered ingot.

[0041] If the divider member 14 transfers heat too rapidly out of thesolidifying metals 16 and 20, the resultant components 38 and 40 may beprone to cracking. Hence, when the divider member 14 is over about 0.25inch thick, it may be desirable to preheat the divider member 14 towithin about 400° C. of the temperature of the molten metals 16 and 20thereby reducing the rate of heat transfer through the divider member14.

[0042] Generally, the divider member 14 has a melting point of at least610° C. The divider member 14 may be an aluminum alloy and preferablycontains at least about 97% aluminum and has a high solidus temperaturesuch as an AA 1000 series alloy. Other suitable materials for thedivider member 14 are composite products containing layers of aluminumalloys, stainless steel, nickel alloys, titanium alloys, magnesiumalloys and combinations thereof that are clad, plated or coated thereto.The chemistry of the divider member 14 may be selected to improve thecorrosion resistance of the final product being cast. For example, theaddition of Zn to the divider member 14 makes the divider member 14 moreelectrochemically negative than at least one of the components 38 and40. This results in galvanic protection, whereby the Zn enriched areas(the divider member 14 and the portion of components 38 and 40 intowhich Zn has diffused) sacrificially protect the more cathodic alloys ofcomponents 38 and 40. The divider member 14 may define a plurality ofsmall holes to allow some wetting between the molten metals 16 and 20without significant intermixing. Alternatively, the divider member 14may be a screen produced from iron, titanium, molybdenum or alloysthereof. Suitable screens are 14×18 mesh about 0.01 inch thick or 32×32mesh about 0.006 inch thick.

[0043] The molten metals 16 and 20 each may be the same or different andeach is preferably an aluminum alloy and may be an alloy of the AAseries 1000, 2000, 3000, 4000, 5000, 6000, 7000, or 8000. Other suitablemetals may include magnesium alloys. For products in which one of themolten metals requires a specialized alloy, the other molten metal mayhave a high scrap alloy content. The low value scrap metal may besimultaneously cast with a thinner layer of the specialized alloy toproduce high value products with a specialized surface such as reflectorsheet, anodized products, architectural products and the like.

[0044] The temperature of the first molten metal 16 may be about equalto the temperature of the second molten metal 20, or the temperatures ofthe first and second molten metals 16 and 20 may differ by up to about150° C. Selection and control of the temperatures of the molten metals16 and 20 during casting is critical, particularly when flux is notused. When no flux is used to remove the oxide on the divider member 14,the selection of molten metal temperatures should be such that thetemperature of the divider member 14 rises above the liquidustemperature of the molten metals 16 and 20.

[0045] When a flux is used or when the material of the divider member 14is selected such that the oxide is disrupted prior to contacting themolten metals 16 and 20 or when the presence of an oxide on the surfacesof the divider member 14 is not detrimental to achieving a strong bond,lower molten metal temperatures may be used and the divider member 14does not necessarily need to reach the liquidus temperatures of themolten metals 16 and 20. In fact, it is desirable that the dividermember 14 does not reach the liquidus temperature(s) because the dividermember 14 remains protected from the molten metals 16 and 20 by themetal that initially solidifies onto the divider member 14. In any case,the molten metal temperatures cannot be so high as to cause completemelting of the divider member 14. Some melting of the divider member 14is acceptable, but complete melting of the divider member 14, evenlocally (i.e. a “burn through”), is undesired. The temperatures for thisprocess depend on the chemistries of the molten metals 16 and 20 and ofthe divider member 14.

[0046] Referring to FIGS. 3 and 4, the present invention may also beused to produce a composite ingot having a single cast layer with alayer of divider metal. In system 2′, the divider member 14 may bedelivered into the mold 4 at a location adjacent to the wall of the mold4 and the molten metal 16 is delivered into the mold 4 via the trough18. The metal 16 begins to solidify in semi-solid zone 28 and ultimatelysolidifies as component 38 bound to the divider member 14 in mannersimilar to the solidification of metal 16 described above to yield aningot 10′. This embodiment of the invention allows for production of aningot 10′ having a solid layer 14 bound to a cast layer 38 which avoidsthe prior art roll bonding processes. Flux may be applied to the surfaceof the divider member 14 which contacts the molten metal 16 in thesystem 2′ or to the surface of pool of molten metal 16 as describedabove. The divider member 14 and component 38 of the ingot 10′ may beselected from the same materials listed above for ingot 10.

[0047] The method of the present invention may also be used to cast morethan two molten metals. For example, in the apparatus 50 shown in FIG.5, two divider members 14 and 52 may be delivered into the direct chillmold 4 while molten metals 16, 20, and 53 are delivered into the moldvia respective troughs 18, 22, and 54. Casting of an ingot 60 from threeseparate molten metals 16, 20, and 53 is performed in a manner similarto that described above. The molten metal 16 solidifies first atlocations 24 (adjacent the mold 4) and 32 (adjacent the divider member14), while molten metal 20 solidifies first at locations 34 (adjacentthe divider member 14) and location 55 (adjacent the divider member 52).Molten metal 53 first solidifies at location 56 (adjacent the dividermember 52) and location 57 (adjacent the mold 4). The solidifying metals16, 20, and 53 form respective semi-solid zones 28, 30 and 58. Thelocations 24, 32, 34, 55, 56, and 57 may be at the same height as eachother or at different heights from the bottom block 12. The resultantproduct includes three cast layers 38, 40, and 62 separated from eachother by divider members 14 and 52 as shown in FIG. 6. The dividermembers 14 and 52 are positioned within the mold in the embodiment ofFIG. 5 similar to divider member 14 of FIG. 1. The distance between thedivider members 14 and 52 is selected based on the desired thicknessesof the components 38, 40, and 62 in the ingot 60 and the size of themold 4. The embodiment shown in FIGS. 5 and 6 relates to simultaneouscasting of three alloys with divider layers interspersed between,thereby creating a five-layer product. This is not meant to be limiting.More than three alloys may be simultaneous cast according to the presentinvention in rectangular configurations or in other configurations byusing other shapes for the mold (e.g. square or oval) and non-planardivider members.

[0048] Additional layers of metal may be bonded to the castmulti-layered ingots 10 and 60 resulting in the products 70 and 80 shownin FIGS. 7 and 8. Product 70 includes the ingot 10 and a pair of metallayers 72 roll bonded to the ingot 10. Product 80 includes the ingot 60with a metal layer 82 roll bonded thereto. Products 70 and 80 each mayhave one or two respective layers 72 or 82. When two layers 72′ areincluded as shown in FIG. 7, the metal of those layers may be the sameor different from each other. The layers 72 and 82 may also bemulti-component products produced according to the present invention orproduced by conventional roll bonding practices.

[0049] One of the advantages of the present invention is borne out whena multi-layered metal ingot produced according to the present inventionis subsequently rolled, for example, into a plate or sheet product. Inconventional roll bonded ingots, the thickness of a clad layer at theends of the ingot oftentimes becomes unacceptably thin during therolling process. The edges of the resulting coil made from the compositeingot must be trimmed and scrapped so that the clad layer is uniformlythick across the width of the coil. Edge trimming of about 4 inches (forabout 3-5% cladding) to about 8 inches (for about 10-15% cladding) istypical for conventional roll bonded brazing sheet. Such scrap lossescan be minimized in the present invention by producing an ingot 90 asshown in FIG. 9 which has an arcuately shaped divider member 92 withmetals 94 and 96 cast on opposing sides thereof. The cast metal 96(corresponding to a conventional clad layer) is thickest at the edges ofthe ingot 90. Upon rolling the ingot 90 to a plate 90′, the dividermember 92′ flattens and the cast metals 94′ and 96′ are substantiallyuniformly thick as shown in FIG. 10. The divider member 92 may betapered or bent into other configurations to locally achieve differingthickness of the metals cast on opposing sides thereof.

[0050] The present invention may also be used to produce cylindricalproducts (e.g., a billet) of multiple alloys. The embodiment of theinvention shown in FIG. 11 and includes an apparatus 100 having acylindrical mold 104 defining a water chamber 106 and a slit 108 throughwhich water is emitted directly onto the surface of an ingot 110emerging from the mold 104. The cast ingot 110 seats on a circularbottom block 112 traveling in the direction of arrow B. A tubulardivider member 114 is fed into the mold 104 and acts as a barrierbetween molten metal 116 fed from trough 118 on the outside of thetubular divider member 114 and molten metal 120 fed from another trough(not shown) on the inside of the tubular divider member 114. Delivery ofthe divider member 114 and movement of the bottom block 112 arecontrolled as described above regarding the apparatus 2. The tubulardivider member 114 may define a longitudinal slot 122 to ease access ofthe molten metal 120 into the divider member 114 during casting.Particularly during startup, the molten metal 120 may be delivered intothe tubular divider member 114 via the slot 122 near the bottom block112 instead of pouring the molten metal 120 into the tubular dividermember 114 which can result in turbulence of the molten metal 120. Theslot 122 is sufficiently narrow (e.g. about 1 to about 20 inches wide,depending on the size of the billet being cast) and may extend down intothe molten pools of metals 116 and 120 to prevent excessive mixingbetween the molten metals 116 and 120 in the vicinity of the slot 122.Molten metal 116 first solidifies adjacent the mold 104 at region 124and molten metal 120 first solidifies adjacent the tubular dividermember 114 at region 126. An annular semi-solid zone 128 forms below thelevel of the first solidification region 124, and a cylindricalsemi-solid zone 130 forms below the level of the region 126. Uponcomplete solidification, the metals 116 and 120 form respective solidcomponents 138 and 140 separate by the tubular divider member 114. Across-section of the billet 110 produced in the apparatus 100 is shownin FIG. 13.

[0051] The present invention provides significant improvements overconventional clad products. The cladding ratio of roll bonded productsis generally a maximum of 35%, i.e. the interface between roll bondedlayers can generally be no greater than about 35% of the distance fromeither face of the ingot. In the present invention, the only limitationon the location of cast layers is that a cast layer is at least about 1inch thick to allow for distribution of molten metal across the width ofthe ingot. The alloys which may be bonded together using the presentinvention are much more numerous than those which may be reliably and/oreconomically roll bonded together. Product quality is improved in theelimination of roll bonding blisters. The productivity of a hot millused to initially breakdown or roll an ingot produced according to thepresent invention is also significantly increased as the many sealingpasses may be eliminated.

[0052] Although the invention has been described generally above, thefollowing particular examples give additional illustrations of theproducts and process steps typical of the present invention.

EXAMPLES 1-3

[0053] In each of Examples 1-3, a sheet of AA 1350 (20 inches wide,0.375 inch thick, and 24 inches long) was positioned in the center of 12inch×22 inch mold spanning the width with a gap of about 1 inch betweenthe edge of the sheet and the mold walls. In each Example, a melt A ofthe alloy listed in Table 1 was poured into the mold on one side of thesheet and a melt B of the alloy B listed in Table 1 was poured into themold on the other side of the sheet. In Example 3, flux was applied tothe side of the sheet which contacted melt A. The metals were cast onopposing sides of the sheet while the bottom block with sheet seatedthereon was lowered at a rate of 2.75 inches per minute. A 12 inch×22inch×about 42 inch ingot having sheet of AA 1350 bonded between a layerof alloy A and a layer of alloy B was produced. TABLE 1 Melt A DividerMelt B Temp. Sheet Temp. Example AA Alloy (° C.) AA alloy AA alloy (°C.) 1 3003 671* 1350  7051** 667 2 3003 664 +/− 3 1350 3005 679 +/− 3 33003 663 +/− 5 1350 with 4343 647 +/− 4 flux on side of melt A

[0054] A block was sectioned from the ingot of Example 1 and was rolled(hot and cold) without any delaminating along the interface between theAA 1350 sheet and the cast layers of AA 3003 and 7051. A photograph of ahorizontal cut through the ingot appears in FIG. 14. A close-upphotomicrograph of the interface between the layers of AA alloy 3003 andmodified AA alloy 7051 showing minimal erosion of the sheet appears inFIG. 15. A portion of the ingot was hot rolled to 0.250 inch (shown inFIG. 16) and subsequently cold rolled to 0.005 inch (shown in FIG. 17).

[0055] A photograph of a horizontal cut through the ingot produced inExample 2 appears in FIG. 18.

[0056] A photograph of a horizontal cut through the ingot produced inExample 3 appears in FIG. 19. Example 3 was repeated without flux and aphotomicrograph of the AA3003/AA1350/AA4343 interface is shown underpolarized light in FIG. 20 after etching in barkers etch to illustratethe microstructural details of the interface.

What is claimed is:
 1. A multi-layered metal product comprising: a layerof a divider metal; and a first metal layer direct chill cast onto oneside of said divider metal layer.
 2. The metal product of claim 1further comprising a second metal layer direct chill cast onto the otherside of said divider metal layer.
 3. The metal product of claim 1,wherein said divider metal comprises an alloy containing at least about97% aluminum.
 4. The metal product of claim 2, wherein said first metallayer and said second metal layer each are an alloy of an AluminumAssociation series selected from the group consisting of 1000, 2000,3000, 4000, 5000, 6000, 7000 and
 8000. 5. The metal product of claim 1,wherein the thickness of said layer of divider metal is about 0.5 toabout 6% of the thickness of said metal product.
 6. The metal product ofclaim 1, wherein the thickness of said layer of divider metal is about 1to about 3% of the thickness of said metal product.
 7. The metal productof claim 1, wherein said metal product is an ingot or a billet.
 8. Themetal product of claim 7, wherein said layer of a divider metal is about0.07 to about 0.25 inch thick.
 9. The metal product of claim 7, whereinsaid layer of a divider metal is over about 0.25 to about 6 inchesthick.
 10. The metal product of claim 2, wherein said metal product is aplate, a sheet or foil.
 11. The metal product of claim 10 furthercomprising an outer metal layer roll bonded to one of said first metallayer and said second metal layer.
 12. The metal product of claim 10further comprising a pair of outer metal layers, each said outer metallayers being roll bonded to one of said first metal layer and saidsecond metal layer.
 13. The metal product of claim 11, wherein saidouter metal layer comprises a pair of metal layers direct chill castonto opposing sides of a divider metal layer.
 14. The metal product ofclaim 2 further comprising at least one other layer of divider metal andat least one other metal layer direct chill cast onto one side of saidother layer of divider metal and one of the first or second metals isdirect chill cast onto the other side of the other layer of dividermetal.
 15. The metal product of claim 2 wherein the melting point of thedivider metal is at least about 5° C. greater than the melting points ofeach of the first metal and the second metal.
 16. A multi-layered metalingot comprising: a layer of a divider metal; a first metal layer bondedto one side of said divider metal layer; and a second metal layer bondedto another side of said divider metal layer, wherein the thickness ofsaid layer of divider metal comprises no more than about 3% of thethickness of said ingot.
 17. The ingot of claim 16, wherein said firstmetal layer and said second metal layer are each direct chill cast ontosaid divider metal layer.
 18. The ingot of claim 16, wherein saiddivider metal comprises an alloy containing at least about 97% aluminum.19. The ingot of claim 16, wherein said first metal layer and saidsecond metal layer each are an alloy of an Aluminum Association seriesselected from the group consisting of 1000, 2000, 3000, 4000, 5000,6000, 7000 and
 8000. 20. The ingot of claim 16, wherein said layer of adivider metal is about 0.07 to about 0.25 inch thick.
 21. The ingot ofclaim 16, wherein said layer of a divider metal is over about 0.25 toabout 6 inches thick.
 22. The ingot of claim 16, further comprising anouter metal layer roll bonded to one of said first metal layer and saidsecond metal layer.
 23. The ingot of claim 22, wherein said outer metallayer comprises a pair of metal layers direct chill cast onto opposingsides of a divider metal layer.
 24. The ingot of claim 16 furthercomprising a pair of outer metal layers, each said outer metal layersbeing roll bonded to one of said first metal layer and said second metallayer.
 25. The ingot of claim 16 further comprising at least one otherlayer of divider metal and at least one other metal direct chill castonto one side of said other layer of divider metal with one of the firstor second metals direct chill cast onto the other side of the otherlayer of divider metal.
 26. The ingot of claim 25, wherein said firstmetal, said second metal, and said at least one other metal are each analloy of an Aluminum Association series selected from the groupconsisting of 1000, 2000, 3000, 4000, 5000, 6000, 7000 and 8000.